Valve lift control device

ABSTRACT

A valve lift control device includes an inner tappet biased toward a low-lift cam pertinent to the opening and the closing of a valve in a low-lift mode acting as one of cams which are arranged on a camshaft being driven rotationally in synchronization with a rotation of an internal combustion engine; an outer tappet arranged outside of the inner tappet and biased toward a high-lift cam pertinent to the opening and the closing of the valve in a high-lift mode among the plurality of cams; and a rotational member being arranged rotationally in a peripheral direction of the inner and outer tappets and including at least one projection member being outwardly projected from a perimeter of the inner tappet and an engagement section engaging with the projection member. The valve lift control device blocks or allows a relative sliding of the inner and outer tappets in an axial direction of the tappet due to rotation of the rotational member in a required range.

TECHNICAL FIELD

The invention relates to a valve lift control device, which controls avalve lift according to operating conditions of an internal combustionengine such as an engine when an intake valve or an exhaust valve of theengine is opened and closed due to a cam via a tappet.

BACKGROUND ART

Generally, with a valve operating system of the internal combustionengine, both of the valve lift and an angular aperture are reduce duringa low-rpm condition. In this way, the velocity of a mixed gas isincreased to improve combustion efficiency. On the other hand, both ofthe valve lift and an overlap are increased during a high-rpm conditionto improve a suction efficiency through the use of an exhaust inertialeffect. In this way, it results in enhancement of fuel economy andimprovement of power of the internal combustion engines.

With the valve operating system as discussed above, the valve liftcontrol device used in conjunction with a valve timing control device isdisclosed in JP-A-1998/507242, for example.

The valve lift control device includes a plurality of cams arranged on acamshaft being driven rotationally in synchronization with a rotation ofan internal combustion engine, an inner tappet movable reciprocally inan axial direction of a valve rod pursuant to a cam profile of alow-lift cam pertinent to the opening and the closing of the valveduring a low-rpm condition (equivalent of a low-lift mode) of the abovecams, an outer tappet arranged outside of the inner tappet and movablereciprocally in an axial direction of a valve rod pursuant to a camprofile of a high-lift cam pertinent to the opening and the closing ofthe valve during a high-rpm condition (equivalent of a high-lift mode),and a movable member arranged in the inner tappet and movable in aradial direction of the inner tappet.

The movable member is moved outwardly in a radial direction of the innertappet due to a hydraulic pressure, which is supplied to a centralsection of the inner tappet in the high-lift mode, to engage whith arecess formed at an inner peripheral section of the outer tappet. As aresult, both tappets are integrated. The hydraulic pressure is reducedin the low-lift mode, and the movable member is moved inwardly in theradial direction of the inner tappet due to a biasing means such asspring and so on to be disconnected from the recess of the outer tappet.As a result, both tappets are separated.

With the conventional valve lift control device, a hydraulic pressurenecessary to engage the movable member with the recess of the outertappet must be however supplied to the central section of the innertappet. The hydraulic system is complicated in construction, and causesa disturbance of operation.

Moreover, JP-A-1998/141030 discloses the same technical information asthe gazette described above.

The invention was made to solve the foregoing problems, and an object ofthe invention is to provide a valve lift control device having a simplestructure to ensure good operating reliability.

DISCLOSURE OF THE INVENTION

A valve lift control device according to the invention comprises aninner tappet biased toward a low-lift cam pertinent to the opening andthe closing of a valve in the low-lift mode acting as one of cams whichare arranged on a camshaft being driven rotationally in synchronizationwith a rotation of an internal combustion engine; an outer tappetarranged outside of the inner tappet and biased toward a high-lift campertinent to the opening and the closing of the valve in the high-liftmode among the plurality of cams; and a rotational member being arrangedrotationally in a peripheral direction of the inner and outer tappetsand including at least one projection member being outwardly projectedfrom a perimeter of the inner tappet and an engagement section engagingwith the projection member, characterized in that a relative sliding ofthe inner and outer tappets in an axial direction of the tappet isblocked or allowed due to a rotation of the rotational member in arequired range. In this way, the valve lift control device is simplyconstituted as compared with the conventional valve lift control device,and facilitates selection between a valve lift during a low-rpmcondition and a valve lift during a high-rpm condition. It is thereforepossible to ensure good operating reliability and good stability in eachparts of the device.

With the above arrangement, the valve lift control device ischaracterized in that the projection member is a rod-shaped memberprojected from the outer periphery of the inner tappet. In this way,since the rod-shaped member acting as the projection member is projectedfrom the outer periphery of the inner tappet, it is possible to ensurethat the rod-shaped member is engaged with and disengaged from anengagement section of the rotational member.

With the above arrangement, the valve lift control device ischaracterized in that the rod-shaped member passes through the interiorof the inner tappet in a radial direction, and that at least one end ofthe rod-shaped member is projected outwardly from the perimeter of theinner tappet in the radial direction. In this way, since the rod-shapedmember acting as the projection member is projected outwardly from theouter periphery of the inner tappet in the radial direction, it ispossible to ensure that the rod-shaped member is engaged with anddisengaged from an engagement section of the rotational member.

With the above arrangement, the valve lift control device ischaracterized in that the rotational member is movable in one directionin two peripheral directions of the inner and outer tappets,respectively, due to a hydraulic pressure. In this way, it is possibleto ensure moving smoothly the rotational member to lock the rod-shapedmember.

With the above arrangement, the valve lift control device ischaracterized in that the rotational member is movable in the otherdirection in two peripheral directions of the inner and outer tappets,respectively, due to a mechanical biasing force. In this way, it ispossible to ensure moving smoothly the rotational member to release alock of the rod-shaped member.

With the above arrangement, the valve lift control device ischaracterized in that the rotational member is movable in bothperipheral directions of the inner and outer tappets, respectively, dueto a hydraulic pressure. In this way, it is possible to ensure movingsmoothly the rotational member to perform a lock of the rod-shapedmember and the release the lock.

With the above arrangement, the valve lift control device ischaracterized in that the rotational member has a recess, which isengaged with the projection member. In this way, when the lock of theprojection member is released due to the rotational member, it ispossible to ensure the relative sliding of the inner and outer tappetsin an axial direction of the tappet within a stroke.

With the above arrangement, the valve lift control device ischaracterized in that the projection has a plane face acting as acontact face, which comes into contact with the rotational member. Inthis way, the rotational member can come into contact with theprojection member with stability.

With the above arrangement, the valve lift control device ischaracterized in that at least one end of the projection member isprojected outwardly from the outer periphery of the inner tappet in aradial direction, and is engaged with a groove formed at an inner faceof a cylindrical aperture, which supports slidably the outer tappet, ofa cylinder head in a sliding direction. In this way, it is possible tocontrol a free rotation of the inner and outer tappets.

With the above arrangement, the valve lift control device ischaracterized in that an edge of a contact face, which comes intocontact with the low-lift cam, of the inner tappet is arranged outsideof an orbit of a cam profile of the low-lift cam, apart from thelow-lift cam. In this way, since the low-lift cam is kept from contactwith the edge of the contact face, which comes into contact with thelow-lift cam, of the inner tappet, it is possible to ensure a smoothsliding of the low-lift cam with respect to the inner tappet.

With the above arrangement, the valve lift control device ischaracterized in that the rotational member has the shape of a sector,at least one thereof is arranged in a holder having a bobbin-shape, andis held rotationally in peripheral directions of the rotational member.In this way, since the rotational member having the shape of a sectorcan be rotated easily within the holder, it is possible to ensure a goodhydraulic response.

With the above arrangement, the valve lift control device ischaracterized in that a stopper controlling a range allowing rotation ofthe rotational member is arranged at a portion of a groove of thebobbin-shaped holder. In this way, since the stopper controls the rangeallowing rotation of the rotational member, it is possible to controlthe relative sliding of the inner and outer tappets in the axialdirection of the tappet with reliability.

With the above arrangement, the valve lift control device ischaracterized in that a torsion-spring, which biases the rotationalmember in one direction of peripheral directions of the inner and outertappets, is provided. Thus, when rotation of the rotational member isperformed due to a hydraulic pressure, and the hydraulic pressure is notsupplied under abnormal conditions, the rotational member can be rotateddue to a mechanical biasing force of the torsion-spring in a safetydirection ensuring a relative position of the tappets.

With the above arrangement, the valve lift control device ischaracterized in that the inner tappet is provided with a slide-bearingmember having a contact face, which comes into contact with the low-liftcam, of the inner tappet and allowing mating with and de-mating from theinner tappet. In this way, it is possible to ensure a smooth sliding ofthe low-lift cam with respect to the inner tappet.

With the above arrangement, the valve lift control device ischaracterized in that a rotational location control means is provided,controlling a relative rotational location between the slide-bearingmember and the inner tappet. In this way, it is possible to prevent theinner tappet from a malfunction, which causes by the high-lift cam whenthe slide-bearing member differ from a standard to cross the orbit ofthe high-lift cam.

With the above arrangement, the valve lift control device ischaracterized in that the slide-bearing member covers with a portion ofthe outer tappet apart from a contact face, which comes into contactwith the high-lift cam, of the outer tappet. In this way, it is possibleto ensure a smooth sliding of the low-lift cam with respect to the innertappet and a smooth sliding of the high-lift cam with respect to theouter tappet.

With the above arrangement, the valve lift control device ischaracterized in that the slide-bearing member is accommodated in agroove formed at a portion of the outer tappet apart from a contactface, which comes into contact with the high-lift cam, of the outertappet, wherein a contact face of the slide-bearing member is flush withthe contact face of the outer tappet. In this way, a base circlediameter of the high-lift cam can be identical to that of the low-liftcam, the cams being arranged on a camshaft.

A valve lift control device according to the invention comprises aninner tappet biased toward a low-lift cam pertinent to the opening andthe closing of a valve in the low-lift mode acting as one of cams whichare arranged on a camshaft being driven rotationally in synchronizationwith a rotation of an internal combustion engine; an outer tappetarranged outside of the inner tappet and biased toward a high-lift campertinent to the opening and the closing of the valve in the high-liftmode among the plurality of cams; a rod-shaped member allowing therelative sliding between the inner and outer tappets in an axialdirection of the tappet within a stroke equivalent to a differencebetween a valve lift due to the low-lift cam and a valve lift due to thehigh-lift cam; a rotational member moving in one direction of peripheraldirections of the inner and outer tappets to lock the rod-shaped memberand accordingly to move integrally the inner and outer tappets in theaxial direction thereof; and a hydraulic mechanism arranged outside ofthe inner tappet to allow the lock and release of the rod-shaped memberdue to the rotational member. In this way, it is not necessary to supplythe hydraulic pressure to the internal of the inner tappet. Since thedevice can be simply constituted, it is possible to ensure goodoperating reliability and good stability in each parts of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross sectional view showing a relation of acam and a tappet in a valve lift control device as embodiment 1according to the invention when a base circle of the cam comes intocontact with the tappet.

FIG. 2 is a plane view of the valve lift control device as shown in FIG.1.

FIG. 3 is a cross sectional view taken along lines IV—IV of FIG. 1.

FIG. 4 is a perspective view showing the valve lift control device asshown in FIG. 1 to FIG. 3.

FIG. 5 is an exploded perspective view of FIG. 4.

FIG. 6(a) to FIG. 6(c) and FIG. 7(a) to FIG. 7(c) are cross sectionalviews taken along lines VI—VI and VII—VII of FIG. 1, respectively, eachshowing a relative position between a cam in a low-lift mode and atappet with time.

FIG. 8 is a longitudinal cross sectional view showing a valve-liftedstate pursuant to a cam profile of a low-lift cam.

FIG. 9 is a perspective view showing the valve lift control device asshown in FIG. 8.

FIG. 10 is a longitudinal cross sectional view showing a valve liftcontrol device in a high-lift mode.

FIG. 11 is a perspective view showing the valve lift control device asshown in FIG. 10.

FIG. 12 is a cross sectional view taken along lines XII—XII of FIG. 10.

FIG. 13(a) to FIG. 13(c) and FIG. 14(a) to FIG. 14(c) are crosssectional views taken along lines XIII—XIII and XIV—XIV of FIG. 10,respectively, each showing a relative position between a cam in ahigh-lift mode and a tappet with time.

FIG. 15 is a longitudinal cross sectional view showing a valve liftcontrol device as embodiment 2 according to the invention.

FIG. 16 is a lateral cross sectional view showing a valve lift controldevice as embodiment 3 according to the invention.

FIG. 17 is a longitudinal cross sectional view showing a valve liftcontrol device as embodiment 4 according to the invention.

FIG. 18 is a plane view showing a valve lift control device as shown inFIG. 17.

FIG. 19 is a cross sectional view taken along lines XIX—XIX of FIG. 18.

FIG. 20 is a cross sectional view showing a rotational member in a valvelift control device as embodiment 5 according to the invention.

FIG. 21 is a cross sectional view showing a holder allowing rotation ofthe rotational member as shown in FIG. 20.

FIG. 22 is an enlarged cross sectional view showing the holder as shownin FIG. 21.

FIG. 23 is a cross sectional view taken along lines XXIII—XXIII of FIG.20, showing the rotational member and the projection member released inthe valve lift control device shown in FIG. 20.

FIG. 24 is a cross sectional view showing the rotational member and theprojection member locked in the valve lift control device shown in FIG.20.

BEST MODES FOR CARRYING OUT THE INVENTION

To explain the invention more in detail, the best modes of carrying outthe invention will be described with reference to the accompanyingdrawings.

Embodiment 1

FIG. 1 is a longitudinal cross sectional view showing a relation of acam and a tappet in a valve lift control device as embodiment 1according to the invention when a base circle of the cam comes intocontact with the tappet. FIG. 2 is a plane view of the valve liftcontrol device as shown in FIG. 1. FIG. 3 is a cross sectional viewtaken along lines IV—IV of FIG. 1. FIG. 4 is a perspective view showingthe valve lift control device as shown in FIG. 1 to FIG. 3. FIG. 5 is anexploded perspective view of FIG. 4. FIG. 6(a) to FIG. 6(c) and FIG.7(a) to FIG. 7(c) are cross sectional views taken along lines VI—VI andVII—VII of FIG. 1, respectively, each showing a relative positionbetween a cam in a low-lift mode and a tappet with time. FIG. 8 is alongitudinal cross sectional view showing a valve-lifted state pursuantto a cam profile of a low-lift cam. FIG. 9 is a perspective view showingthe valve lift control device as shown in FIG. 8. FIG. 10 is alongitudinal cross sectional view showing a valve lift control device ina high-lift mode. FIG. 11 is a perspective view showing the valve liftcontrol device as shown in FIG. 10. FIG. 12 is a cross sectional viewtaken along lines XII—XII of FIG. 10. FIG. 13(a) to FIG. 13(c) and FIG.14(a) to FIG. 14(c) are cross sectional views taken along linesXIII—XIII and XIV—XIV of FIG. 10, respectively, each showing a relativeposition between a cam in a high-lift mode and a tappet with time.Moreover, in the drawings, for reasons of expediency, a camshaft side isdefined as an upper side, and a valve side is defined as a lower side.

In the drawings, a reference numeral 1 denotes a cylinder head of aninternal combustion engine (not shown), and a reference numeral 2denotes an intake valve or an exhaust valve (hereafter, referred brieflyas a valve) arranged at the cylinder head 1. A reference numeral 3denotes a valve rod supporting the valve 2, and a reference numeral 4denotes a camshaft driven rotationally in synchronization with arotation of the internal combustion engine. A reference numeral 5denotes a low-lift cam fixed on the camshaft 4 and used for controllinga valve lift in a low-lift mode corresponding to a low-rpm condition ofthe internal combustion engine. A reference numeral 6 denotes a pair ofhigh-lift cams fixed on both sides of the low-lift cam 5 fixed on thecamshaft 4 and used for controlling a valve lift in a high-lift modecorresponding to a high-rpm condition of the internal combustion engine.A reference numeral 7 denotes a base circle having a circularcross-sectional shape and used as the reference of the low-lift cam 5and the high-lift cam 6. A cam profile of the low-lift cam 5 has a firstbump section 8 formed at a part of the base circle 7. A cam profile ofthe high-lift cam 6 has a second bump section 9 formed at a part of thebase circle 7 and larger than the first bump section 8.

A reference numeral 10 denotes an inner tappet movable reciprocally inan axial direction of the valve rod 3. The inner tappet 10 is acylindrical member in general including a disc top section 10 a, whichcomes into contact with the cam profile of the high-lift cam 6, and abody section 10 b having a smaller diameter than the top section 10 a. Athrough-hole 10 c allowing occupancy of a rod-shaped member discussedlater is formed at an outer periphery of the inner tappet 10 so as to besymmetrical about the midpoint of the axis of the inner tappet 10. Anouter tappet 11 is co-axially arranged outside of the inner tappet 10,and movable reciprocally in the axial direction of the valve rod 3. Theouter tappet 11 is a cylindrical member in general. The outer tappet 11includes a central accommodation hole 11 a accommodating the innertappet 10 therein, a ring-shaped upper face 11 b enclosing the centralaccommodation hole 11 a and coming into contact with the cam profile ofthe low-lift cam 5, and a lower opening section 11 c. The outer tappet11 is accommodated slidably in a cylindrical hole 1 a of the cylinderhead 1. A pair of through-holes 11 d is formed at an outer periphery ofthe outer tappet 11, allowing occupancy of a pin discussed later in astate of projecting outwardly ends of the pin from the through holes 11c in association with the through hole 10 c of the inner tappet 10. Thethrough-hole 11 d of the outer tappet 11 has a cross sectional profileas distinct from the through-hole 10 c of the inner tappet 10, theprofile being long in an axial direction of the valve rod 3. A length ofthe profile is identical to a lift-stroke between the low-lift cam 5 andthe high-lift cam 6. A hydraulic supply port 11 e being connected with ahydraulic port discussed later is formed at the outer periphery of theouter tappet 11. A reference numeral 12 denotes a pin acting as arod-shaped member penetrating the through-hole 10 c of the inner tappet10 and the through-hole lid of the outer tappet 11 to protect a relativerotation between both of tappets.

A reference numeral 13 denotes a case having a cylindrical shape ingeneral, the case being co-axially accommodated from the lower openingsection 11 c in the outer tappet 11 in order to arrange a rotationalmember discussed later in a place between the case 13 and the outertappet 11. The case 13 has an upper-opening structure having no upperwall and being the reverse equivalent of the outer tappet 11. Aselection vane-accommodation groove 15 is constituted by an outerperipheral wall 13 a, an inner peripheral wall 13 b disposed inside ofthe outer peripheral wall 13 a, and an intermediate bottom 13 c definedbetween the both of the walls. A communication wall 13 d communicatingthe outer peripheral wall 13 a with the inner peripheral wall 13 b isformed so as to extend inwardly from a part of the outer peripheral wall13 a in a radial direction of the case 13. A pin-accommodation groove 16allowing occupancy of a pin 12 is formed at the case 13, the pin 12passing through a center of the case 13 to cross over the selectionvane-accommodation groove 15. The pin-accommodation groove 16 has across sectional profile, which is long in the axial direction of thevalve rod 3. A bottom of the pin-accommodation groove 16 is formed to bedeeper than the intermediate bottom 13 c constituting the selectionvane-accommodation groove 15. A hydraulic supply port 13 e supplying thehydraulic pressure of one side of the communication wall 13 d to theselection vane-accommodation groove 15 is arranged at an outer peripheryof the case 13. A ring-shaped spring-accommodation groove 18 allowingoccupancy of a spring 17 discussed later is formed at the intermediatebottom 13 c of the case 13 as shown in FIG. 1.

A selection vane 14 acting as a rotational member is accommodated in theselection vane-accommodation groove 15 of the case 13 as shown in FIG.6. The selection vane 14 has a profile that a part of doughnut-shapedmember is cut off. One end 14 a of the selection vane 14 allowsapproaching one side of the communication wall 13 d. A return spring 19is arranged between the other end 14 b of the selection vane 14 and theother side of the communication wall 13 d, the return spring 19 actingas a coil spring biasing acting as a coil spring biasing both sides tokeep both sides separated. A pair of recesses 20 allowing occupancy ofthe pin 12 as a means connecting the inner tappet 10 with the outertappet 11 is formed at a lower edge 14 c of the selection vane 14 to besymmetrical about the midpoint of the axis of the selection vane 14.

The body section 10 b of the inner tappet 10 is co-axially accommodatedinside of the inner peripheral wall 13 b of the case 13 and the innertappet 10 is reciprocally movable in the axial direction of the valverod 3. A circular-shaped holding plate 21 is fixedly arranged at a loweredge of the body section 10 b of the inner tappet 10. A shim 22 actingas a gap-adjustment member adjusting a gap between the cam profile andthe tappet is fixedly arranged at a center of the bottom of the bodysection 10 b. The spring 17 is arranged in a space between the lowerside of the intermediate bottom 13 c of the case 13 and the holdingplate 21 fixed at the inner tappet 10. The spring 17 allows following anoperation of the high-lift cam 6 due to the outer tappet 11 when theinternal combustion engine (not shown) is operated at a low-rpm, andprevents the occurrence of an abnormal condition.

A spring 23 is arranged between a circular-shaped holding plate 3 aarranged at the upper end of the valve rod 3 and a spring-receiving face1 b of the cylinder head 1 as shown in FIG. 1. The spring 23 biases thevalve rod 3 toward closing the valve 2 arranged fixedly at the lower endof the valve rod 3 at all times. In this way, only the inner tappet 10connected co-axially with the valve rod 3 or the outer tappet 11integral with the inner tappet 10 can come into contact with thelow-lift cam 5 or the high-lift cam 6 which is located above. In FIG. 2,a reference numeral 24 denotes a hydraulic port arranged within thecylinder head 1. The hydraulic port 24 supplies a hydraulic pressure ofan oil pump (not shown) to a space, which is defined between the one end14 a of the selection vane 14 accommodated in the selectionvane-accommodation groove 15 and the communication wall 13 d, via thehydraulic supply port 11 e of the outer tappet 11 and the hydraulicsupply port 13 e of the case 13. A pair of rotation-protection grooves25 is formed at mutual facing positions of an inner periphery of thecylindrical hole 1 a of the cylinder head 1. The grooves 25 are engagedwith the front end of the pin 12, which is projected from thethrough-hole 11 d of the outer tappet 11, to control a free rotation ofthe outer tappet 11 and the inner tappet 10 in the cylindrical hole 1 a.

Next, an operation will be described.

First, when the internal combustion engine (not shown) is operated atthe low-rpm, the end 14 b of the selection vane 14 is pressed along theselection vane-accommodation groove 15 of the case 13 due to a biasingforce of the return spring 19 based on a control signal from a controldevice (not shown) as shown in FIG. 3. In this way, the selection vane14 is rotated in a peripheral direction of the case 13 until the end 14a of the selection vane 14 comes into contact with one side of thecommunication wall 13 d. In such a state of rotation, the recess 20 ofthe selection vane 14 is located above the pin accommodation groove 16of the case 13, and the pin 12 arranged in the pin accommodation groove16 is movable reciprocally between the recess 20 and the pinaccommodation groove 16. In this case, the selection vane 14 allows therelative movement of the inner tappet 10 and the outer tappet 11 withinthe range of movement of the pin 12.

Here, as shown in FIG. 6(a), the base circle 7 of the cam profile of thelow-lift cam 5 comes into contact with the top section 10 a of the innertappet 10. On the other hand, the base circle 7 of the cam profile ofthe high-lift cam 6 comes into contact with the upper face 11 b of theouter tappet 11.

Next, as shown in FIG. 6(b), FIG. 6(c) and FIG. 7(a) to FIG. 7(c), whenthe camshaft 4 is rotated, the cam profile of the low-lift cam 5 is slidover the top section 10 a of the inner tappet 10. On the other hand,when the camshaft 4 is rotated, the cam profile of the high-lift cam 6is slid over the upper face 11 b of the outer tappet 11.

Here, the inner tappet 10 gradually moves upward pursuant to the camprofile of the low-lift cam 5 with respect to the outer tappet 11 by adifferential lift-stroke defined between the cam profiles of cams 5 and6. On the other hand, the outer tappet 11 gradually moves downwardpursuant to the cam profile of the high-lift cam 6 with respect to theinner tappet 10. That is, as shown in FIG. 8 and FIG. 9, the lift-strokeproduced due to the cam profile of the high-lift cam 6 is absorbed bythe spring 17 at the low-rpm. In this way, the valve 2 is opened by thelift-stroke pursuant to the cam profile of the low-lift cam 5.

Next, when the internal combustion engine (not shown) is operated at thehigh-rpm, a state shown in FIG. 3 is changed to a state shown in FIG. 11and FIG. 12 based on a control signal from a control device (not shown).In other words, a hydraulic pressure is supplied from the hydraulic port24 to a space, which is defined between the one end 14 a of theselection vane 14 accommodated in the selection vane-accommodationgroove 15 and the communication wall 13 d, via the hydraulic supply port11 e of the outer tappet 11 and the hydraulic supply port 13 e of thecase 13. In this way, the selection vane 14 is rotated against thebiasing force of the return spring 19 in a direction (indicated by anarrow A) of the peripheral directions of the case 13 in the selectionvane-accommodation groove 15, and the end 14 b of the selection vane 14is close to the other side of the communication wall 13 d. At this time,a part of the outer periphery of the rod 12 b of the pin 12 deviatesfrom the recess 20 of the selection vane 14, and comes into contact withthe lower edge 14 c of the selection vane 14. In such a state, theselection vane 14 locks the inner tappet 10 and the outer tappet 11using the pin 12 in order to integrate the inner tappet 10 with theouter tappet 11.

Next, when the camshaft 4 is rotated as shown in FIG. 13 (a) to FIG.13(c) and FIG. 14(a) to FIG. 14(c), the inner tappet 10 is not operatedpursuant to the cam profile of the low-lift cam 5 because the innertappet 10 is integral with the outer tappet 11. The inner tappet 10 andthe outer tappet 11 are operated pursuant to the cam profile of thehigh-lift cam 6. That is, as shown in FIG. 10, the cam profile of thelow-lift cam 5 is not transmitted to the inner tappet 10, and the valve2 is opened by the lift-stroke pursuant to the cam profile of thehigh-lift cam 6.

Next, when a high-rpm operation of the internal combustion engine (notshown) is changed to a low-rpm operation, a hydraulic pressure suppliedto the selection vane-accommodation groove 15 is reduced. The selectionvane 14 is further rotated due to the biasing force of the return spring19 in the other direction (inverted direction arrow A of FIG. 12) of theperipheral directions of the case 13. The one end 14 a of the selectionvane 14 then comes into contact with the other side of the communicationwall 13 d. As shown in FIG. 6(a), the recess 20 of the selection vane 14and the pin 12 are arranged in the axial directions of the tappets 10and 11 to return the tappets 10 and 11 to a state of allowing sliding ofthe tappets in the axial directions.

As described above, according to the embodiment 1, since the pin 12acting as the rod-shaped member and the selection vane 14 acting as therotational member are arranged, the valve lift control device is simplyconstituted as compared with the conventional valve lift control device.The valve lift control device facilitates selection between a valve liftduring a low-rpm condition and a valve lift during a high-rpm condition.

It is therefore possible to ensure good operating reliability and goodstability in each parts of the device.

With the embodiment 1, the doughnut-shaped member having a cut-offportion is used as the selection vane 14. Alternatively, at least onefan-shaped member may be used as the selection vane 14.

With the embodiment 1, the return spring 19 is used as a coil spring.Alternatively, a torsion-spring may be used as the spring.

With the embodiment 1, the rod 12 b of the pin 12, which comes intocontact with the lower edge 14 c of the selection vane 14, has thecylindrical shape. A contact face of the rod 12 b may be formed as aplane face. In this way, it is possible to ensure good stability withrespect to contact between the pin 12 and the selection vane 14. In thiscase, the rod 12 b may be a T-shaped or rectangular in cross section,and the invention is not limited to these profiles.

With the embodiment 1, the rotation of the selection vane 14 isperformed due to an oil pressure as the hydraulic pressure. Thehydraulic pressure is not limited to the oil pressure, and everyhydraulic transmission medium can be used without any limitation.

Embodiment 2

FIG. 15 is a longitudinal cross sectional view showing a valve liftcontrol device as embodiment 2 according to the invention. Components ofthe embodiment 2 common to those of the embodiment 1 are denoted by thesame reference numerals and further description will be omitted.

The embodiment 2 is characterized in that a spring-receiving face 1 c isco-axially arranged outside the spring-receiving face 1 b of thecylinder head 1. Moreover, a tolerance space having a distance forstroke of the spring 17 longer than the embodiment 1 is defined betweenthe spring-receiving face 1 c and the bottom of the case 13 and thespring 17 having a diameter than larger than the embodiment 1 isarranged within the tolerance space.

With the embodiment 1, the spring 17 produces an insufficient load inthe tolerance space, and there is a possibility the outer tappet 11 issurged. On the other hand, as shown in FIG. 15, the spring 17 of theembodiment 2 is arranged in the tolerance space having the distance forstroke of the spring 17 longer than the embodiment 1. With theembodiment 2, the spring 17 therefore produces a sufficient load in thetolerance space, and it is possible to prevent the outer tappet 11 fromsurging.

Embodiment 3

FIG. 16 is a lateral cross sectional view showing a valve lift controldevice as embodiment 3 according to the invention. Components of theembodiment 3 common to those of the embodiment 1 are denoted by the samereference numerals and further description will be omitted.

The embodiment 3 is characterized in that a hydraulic pressure is usedfor rotating the selection vane 14 in a direction indicated by an arrowB in conjunction with the biasing force of the return spring 19. Thereturn spring 19 is used when the high-rpm operation of the internalcombustion engine (not shown) is changed to the low-rpm operation withthe embodiment 1. That is, as shown in FIG. 16, a second hydraulicsupply port 11 f is arranged at the outer periphery of the outer tappet11. A second hydraulic supply port 13 f, which communicates with theselection vane-accommodation groove 15 positioned at the other side ofthe communication wall 13 d, is arranged at the outer periphery of thecase 13. A hydraulic supply passage 13 g is arranged between the secondhydraulic supply port 13 f and the outer periphery of the case 13, whichcorresponds to the second hydraulic supply port 11 f of the outer tappet11.

As described above, according to the embodiment 3, the selection vane14, which is rotated due to the mechanical biasing force and thehydraulic pressure, is used as a component. It is possible to locksmoothly the pin 12 due to the selection vane 14 and release smoothlythe lock of the pin 12. Even if the hydraulic pressure is not suppliedaccidentally due to the occurrence of some event, it is possible toswitch safely between locking and releasing due to the mechanicalbiasing force.

Embodiment 4

FIG. 17 is a longitudinal cross sectional view showing a valve liftcontrol device as embodiment 4 according to the invention. FIG. 18 is aplane view showing a valve lift control device as shown in FIG. 17. FIG.19 is a cross sectional view taken along lines XIX—XIX of FIG. 18.Components of the embodiment 4 common to those of the embodiment 1 aredenoted by the same reference numerals and further description will beomitted.

The embodiment 4 is characterized in that a peripheral section of thetop section 10 a of the inner tappet 10 is arranged outside the orbit ofthe cam profile of the low-lift cam 5, apart from the low-lift cam 5.

The arrangement can prevent the cam profile of the low-lift cam 5 fromcoming into contact with the peripheral section of the top section 10 aat the maximum lift-stroke of the low-lift cam 5.

That is, with the embodiment 4, a guide shim 26 acting as theslide-bearing member undergoing a sliding of the low-lift cam 5 ismounted detachably at an upper section of the inner tappet 10 as shownin FIG. 17 to FIG. 19. The guide shim 26 includes a sliding section 26 aformed in parallel to the orbital face of the cam profile of thelow-lift cam 5 and extending in a direction orthogonal to the axialdirection of the camshaft 4, and a base section 26 b formed at a centrallower side of the sliding section 26 a and mated with a recess 10 dformed at the upper section of the inner tappet 10 in place of the topsection 10 a. An upper face of the sliding section 26 a is defined as asliding face 26 c undergoing a sliding of the low-lift cam 5, and thesliding face 26 c has a rectangular shape extending in a directionorthogonal to the axial direction of the camshaft 4. In this way, sincea lateral edge of the sliding face 26 c is located outside the orbit ofthe cam profile of the low-lift cam 5, it is possible to prevent thelateral edge of the sliding face 26 c from coming into contact with thelow-lift cam 5.

With the embodiment 4, it is possible to prevent the low-lift cam 5 fromcoming into contact with the peripheral section of the top section 10 aof the inner tappet 10, and to ensure a smooth sliding of the low-liftcam 5 with respect to the inner tappet 10.

With the embodiment 4, the lower section of the sliding section 26 a ofthe guide shim 26 is accommodated in an accommodation groove 11 g formedat the upper face 11 b of the outer tappet 11. A portion, which is apartfrom a contact face undergoing a sliding of the high-lift cam 6, in theupper face 11 b of the outer tappet 11 is substantially covered with thelower section of the sliding section 26 a. In this case, when the guideshim 26 is rotated on the orbit of the high-lift cam due to theoccurrence of some event, it is impossible to perform the smooth slidingof the low-lift cam. Members such as Pins, keys and so on, or techniquesuch as spline, serration and so on are used as a rotational locationcontrol means in order to prevent the smooth sliding. However, theinvention is not limited to the rotational location control means above.

With the embodiment 4, the sliding face 26 c of the guide shim 26 isprojected upwardly from the upper face 11 b of the outer tappet 11. Inthis case, a thickness of the sliding section 26 a is available to afeature in which the base circle diameter of the high-lift cam isdifferent from that of the low-lift cam. The sliding section 26 a cantherefore have a high degree of flexibility in thickness.

Embodiment 5

FIG. 20 is a cross sectional view showing a rotational member in a valvelift control device as embodiment 5 according to the invention. FIG. 21is a cross sectional view showing a holder allowing rotation of therotational member as shown in FIG. 20. FIG. 22 is an enlarged crosssectional view showing the holder as shown in FIG. 21. FIG. 23 is across sectional view taken along lines XXIII—XXIII of FIG. 20, showingthe rotational member and the projection member released in the valvelift control device shown in FIG. 20. FIG. 24 is a cross sectional viewshowing the rotational member and the projection member locked in thevalve lift control device shown in FIG. 20. Components of the embodiment5 common to those of the embodiment 1 are denoted by the same referencenumerals and further description will be omitted.

The embodiment 5 is characterized in that a stopper-pin-receiving face30, which locks an operation of the pin 12, is arranged at a part of therecess 20 of the rotational member. That is, with the embodiment 1 andso on, the lower edge 14 c of the selection vane 14 defined as thesliding face of the rotational member functions as astopper-pin-receiving face. On the other hand, with the embodiment 5,the sliding face and the stopper-pin-receiving face of the rotationalmember are divided into two ways. In this way, it is possible to ensuregood operating reliability.

With the embodiment 5, a holder 31 allowing rotation of the rotationalmember has a bobbin-shape, which is simple, in consideration of themachinability of the rotational member as shown in FIG. 21 and FIG. 22.The holder 31 includes a cylindrical section 31 a, a rotationalmember-accommodation groove 31 b formed along an outer periphery of thecylindrical section 31 a to accommodate the rotational member, and apin-accommodation groove 31 c extended in an axial direction of thecylindrical section 31 a to pass through the cylindrical section 31 a.The cylindrical section 31 a of the holder 31 accommodates the innertappet 10 so as to allow sliding of the inner tappet 10 in the axialdirection. An U-letter shaped spring retainer 32 in cross section isarranged at a periphery of a bottom of the holder 31. The springretainer 32 accommodates the return spring 19 acting as thetorsion-spring, which biases the rotational member against the hydraulicpressure.

With the embodiment 5, two fan-tailed selection vanes 33 and 34constitute the rotational member. In this way, an area of a hydraulicpressure undergoing face is larger than that of the embodiment 1 and soon as a length of the tappet is shorten. Therefore, it is possible toensure a good hydraulic response.

Next, an operation will be described.

First, when the internal combustion engine (not shown) is operated at alow-rpm, as shown in FIG. 23, a hydraulic pressure is not supplied to aspace defined between the accommodation groove 31 b of the holder 31 andthe inner wall face of the outer tappet 11. Therefore, the selectionvanes 33 and 34 are rotated in a direction indicated by the arrow A dueto the biasing force of the return spring 19, and the selection vane 34comes into contact with one wall face 35 a of the stopper 35. In such astate, the pin 12 is moved freely within the recess 20 of the selectionvane 33 to allow a relative sliding of the inner tappet 10 and the outertappet 11 in an axial direction of the tappet.

Next, when the internal combustion engine (not shown) is operated at ahigh-rpm in FIG. 24, a hydraulic pressure is supplied to a space definedbetween the accommodation groove 31 b of the holder 31 and the innerwall face of the outer tappet 11 via the hydraulic supply port 11 e.Therefore, the selection vanes 33 and 34 are rotated in a directionindicated by the arrow B against the biasing force of the return spring19, and the pin 12 is engaged with the stopper-pin-receiving face 30formed at a part of the recess 20. In such a state of lock, it ispossible to protect a relative rotation between the inner tappet 10 andthe outer tappet 11 in the axial direction of the tappet.

As described above, according to the embodiment 5, the stopper-pinreceiving face 30 is arranged at a part of the recess 20. Thus, it isnot necessary to mount the pin 12 on the sliding face (the lower edge 14c) of the rotational member as in the case of the embodiment 1 and soon. In this way, it is possible to shorten a dimension L at least by alength corresponding to a diameter of the pin 12, and to save weight ofthe valve lift control device.

Moreover, with the embodiment 5, two fan-tailed selection vanes 33 and34 divided constitute the rotational member. Alternatively, therotational member may be constituted by a single member or may bedivided into three parts or more.

INDUSTRIAL APPLICABILITY

As apparent from the foregoing, when the valve lift control device isused in conjunction with a valve timing control device, the valve liftcontrol device can be controlled effectively as compared with a singleuse in order to enhance fuel economy and to produce a high-power.

What is claimed is:
 1. A valve lift control device, comprising: an innertappet biased toward a low-lift cam pertinent to the opening and theclosing of a valve in the low-lift mode acting as one of cams which arearranged on a camshaft being driven rotationally in synchronization witha rotation of an internal combustion engine; an outer tappet arrangedoutside of the inner tappet and biased toward a high-lift cam pertinentto the opening and the closing of the valve in the high-lift mode amongthe plurality of cams; and a rotational member being arrangedrotationally in a peripheral direction of the inner and outer tappetsand including at least one projection member being outwardly projectedfrom a perimeter of the inner tappet and an engagement section engagingwith the projection member, characterized in that a relative sliding ofthe inner and outer tappets in an axial direction of the tappets isblocked or allowed due to a rotation of the rotational member in arequired range.
 2. A valve lift control device according to claim 1,characterized in that the projection member is a rod-shaped memberprojected from the outer periphery of the inner tappet.
 3. A valve liftcontrol device according to claim 2, characterized in that therod-shaped member passes through the interior of the inner tappet in aradial direction, and that at least one end of the rod-shaped member isprojected outwardly from the perimeter of the inner tappet in the radialdirection.
 4. A valve lift control device according to claim 1,characterized in that the rotational member is movable in one directionin two peripheral directions of the inner and outer tappets,respectively, due to a hydraulic pressure.
 5. A valve lift controldevice according to claim 4, characterized in that the rotational memberis movable in the other direction in two peripheral directions of theinner and outer tappets, respectively, due to a mechanical biasingforce.
 6. A valve lift control device according to claim 1,characterized in that the rotational member is movable in bothperipheral directions of the inner and outer tappets, respectively, dueto a hydraulic pressure.
 7. A valve lift control device according toclaim 1, characterized in that the rotational member has an recess,which is engaged with the projection member.
 8. A valve lift controldevice according to claim 1, characterized in that the projection has aplane face acting as a contact face, which comes into contact with therotational member.
 9. A valve lift control device according to claim 1,characterized in that at least one end of the projection member isprojected outwardly from the outer periphery of the inner tappet in aradial direction, and is engaged with a groove formed at an inner faceof a cylindrical aperture, which supports slidably the outer tappet, ofa cylinder head in a sliding direction.
 10. A valve lift control deviceaccording to claim 1, characterized in that an edge of a contact face,which comes into contact with the low-lift cam, of the inner tappet isarranged outside of an orbit of a cam profile of the low-lift cam, apartfrom the low-lift cam.
 11. A valve lift control device according toclaim 1, characterized in that the rotational member has the shape of asector, at least one thereof is arranged in a holder having abobbin-shape, and is held rotationally in peripheral directions of therotational member.
 12. A valve lift control device according to claim11, characterized in that a stopper controlling a range allowingrotation of the rotational member is arranged at a portion of a grooveof the bobbin-shaped holder.
 13. A valve lift control device accordingto claim 11, characterized in that a torsion-spring, which biases therotational member in one direction of peripheral directions of the innerand outer tappets, is provided.
 14. A valve lift control deviceaccording to claim 1, characterized in that the inner tappet is providedwith a slide-bearing member having a contact face, which comes intocontact with the low-lift cam, of the inner tappet and allowing matingwith and de-mating from the inner tappet.
 15. A valve lift controldevice according to claim 14, characterized in that the slide-bearingmember covers with a portion of the outer tappet apart from a contactface, which comes into contact with the high-lift cam, of the outertappet.
 16. A valve lift control device according to claim 14,characterized in that the slide-bearing member is accommodated in agroove formed at a portion of the outer tappet apart from a contactface, which comes into contact with the high-lift cam, of the outertappet, wherein a contact face of the slide-bearing member is flush withthe contact face of the outer tappet.
 17. A valve lift control device,comprising: an inner tappet biased toward a low-lift cam pertinent tothe opening and the closing of a valve in the low-lift mode acting asone of cams which are arranged on a camshaft being driven rotationallyin synchronization with a rotation of an internal combustion engine; anouter tappet arranged outside of the inner tappet and biased toward ahigh-lift cam pertinent to the opening and the closing of the valve inthe high-lift mode among the plurality of cams; a rod-shaped memberallowing the relative sliding between the inner and outer tappets in anaxial direction of the tappet within a stroke equivalent to a differencebetween a valve lift due to the low-lift cam and a valve lift due to thehigh-lift cam; a rotational member moving in one direction of peripheraldirections of the inner and outer tappets to lock the rod-shaped memberand accordingly to move integrally the inner and outer tappets in theaxial direction thereof; and a hydraulic mechanism arranged outside ofthe inner tappet to allow the lock and release of the rod-shaped memberdue to the rotational member.